During every minute of the day, every day, a volcano is erupting somewhere on Earth. Actually, it’s more like a dozen. Or two. Satellites capture much of this activity, and we try to highlight as many eruptions as possible, but for one reason or another (like clouds) some of them fall through the cracks. Here are a handful from the past few weeks:
Natural-color satellite image of Mount Etna, Italy; acquired on September 18, 2011, by the Advanced Land Imager (ALI). Credit: NASA Earth Observatory/EO-1 Science Team.
Natural-color satellite image of Bezymianny Volcano, Russia; acquired on September 20, 2011 by the Advanced Land Imager (ALI). Credit: NASA Earth Observatory/EO-1 Science Team.
False-color satellite image of Kizimen Volcano, Russia; acquired on September 21, 2011, by the Advanced Spaceborne Thermal Reflection and Emission Radiometer (ASTER). Credit: NASA Earth Observatory and the NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team.
Natural-color satellite image of Ambrym Volcano, Vanuatu; acquired on September 23, 2011, by the Advanced Land Imager (ALI). Credit: NASA Earth Observatory/EO-1 Science Team.
Once upon a time Landsat images were expensive (Landsat 7 data was $600 per scene, and the earlier satellites were even pricier) and difficult to find. Now the data—which dates to 1972—is free, and reasonably easy (or at least not painfully difficult) to browse and download from the Global Visualization Viewer, or even the Google Earth Engine (which still has some rough edges).
There are some amazing things buried in the archive, like this natural-color image of an eruption at Rabaul. According to the Global Volcanism Program the activity at the time was “continuous, forceful emissions of thick, light-to-dark gray ash clouds.”
Callan Bentley of Mountain Beltway posted a photo of the Chesapeake that’s a nice complement to the view from space we published last night. I live in the Anacostia River watershed, which feeds into the Chesapeake, and all the nearby streams have been brown since Hurricane Irene hit three weeks ago. The Bay is probably going to be muddy for a while.
You can see how things progress with twice-daily satellite views of the Bay via the image “subset” centered on the Chesapeake Lighthouse. Unfortunately, it’s been cloudy the past few days, but there’s a chance there will be a clear shot by early next week—the forecast for Monday is “mostly sunny.”
Two more images that don’t quite fit on the main site: Nabro Volcano and the Riley Road Fire near Houston.
Nabro VolcanoThis long-dormant Eritrean volcano began erupting in June, but it’s so remote (at least for western media and scientists) that there’s been no news from the area for months. Unfortunately it’s often been cloudy, so we haven’t gotten any good satellite imagery, either. The best recent imagery is this false-color image (vegetation is red), which shows activity has ceased, although there may be a slight hint of gas emissions near the vent. We’re still trying for better imagery, and will post anything we get in our Volcanoes and Earthquakes section.
Riley Road FireCloser to NASA’s home is this photograph from last week of smoke from the Riley Road Fire, which burned 18,960 acres (7,670 hectares) near Houston, Texas (visible in the upper right corner). It was taken by an astronaut aboard the International Space Station, who could probably see his (the Expedition 28 crew is all male) house at the time.
A time-lapse sequence from the International Space Station taken on September 3, 2011. The station starts above Northern Africa, then passes over the Mediterranean Sea and Turkey, followed by the Black and Caspian Seas, the Great Steppe, and finally Mongolia and Lake Baikal.
Sometimes I’ll find a surprise in a satellite image. In this case, kilometer-tall letters that spell out “LUECKE” near Austin, TX (Near the Bastrop Fire):
Although this could have just been a curiosity for passing pilots and astronauts, it turns out that Johnson Space Center scientists used the letters to estimate the maximum resolution of cameras aboard the Space Shuttle.
We also made an empirical estimate of spatial resolution for lower contrast vegetation boundaries. By clearing forest so that a pattern would be visible to landing aircraft, a landowner outside Austin, Texas (see also aerial photo in Lisheron 2000), created a target that is also useful for evaluating spatial resolution of astronaut photographs. The forest was selectively cleared in order to spell the landowner’s name ‘LUECKE’ with the remaining trees (figure 10). According to local surveyors who planned the clearing, the plan was to create letters that were 3100 ´ 1700 ft (944.9 ´ 518.2 m). Photographed at a high altitude relative to most Shuttle missions (543 km) with a 250-mm lens, Formula 3 predicts that each pixel would represent an area 28.6 ´ 36.0 m on the ground (table 5). When original film was digitised at 2400 ppi (10.6 mm/pixel), letters correspond to 29.4 ´ 18.8 pixels for a comparable pixel size of 27 – 32 m.
It’s reminiscent of the map of Italy I saw on a hillside near Castellucio, in the Apennines, or even the Nazca Lines. What other examples of landscaping visible from space are out there?